This invention relates generally to electronic control and monitoring of certain jet engine performance parameters and more specifically to electronic control of jet engine overspeed and overthrust.
Under some operating conditions, multiple engine aircraft may be susceptible to lateral stability problems when one engine erroneously produces more than the commanded level of thrust. For example, one such operating condition is that of the aborted takeoff, and more specifically, runway procedures following an aborted takeoff.
To minimize the effects of an engine failing during such flight conditions, specific techniques are used to increase the aircrafts tolerance to uncommanded asymmetric thrust. Aircraft engines typically include control features that detect and respond with control action when engine rotor speeds reach the maximum level to which the engines are certified. Other aircraft include systems that sense a difference in side-to-side engine thrust and then automatically adjust rudder position to compensate for the fan speed differences.
Such aircraft stability control techniques are directed to lateral stability control in flight, but are limited during landing or aborted take-off. It would be desirable to address uncommanded engine overthrust detection and control by adding test conditions to known overspeed detection schemes, thereby providing improved reliability in the detection and control of uncommanded overthrust conditions.
In an exemplary embodiment, a control system senses jet engine fan speed in excess of a fan speed computed from an aircraft throttle input and responds by adding test conditions to a main central processing unit (CPU) and adding test conditions to an independent overspeed module that provide additional protection from main CPU computational errors. The test conditions include interpretation of sensor data relating to the speed of an engine and further include modeling capability for sensor data when actual sensor data is not within a predetermined tolerance. Logic and data tables are used to compare measured/computed conditions to desired conditions and if an anomaly is detected, an engine fuel cutback device is engaged reducing fuel flow to the engine which is not functioning as desired.